In place of \(w_1\)  and \(w_2\)  we may turn to \(w=\frac{1}{2}(w_1+w_2)\)  and \(u=\frac{1}{2}(w_1-w_2)\)  as coordinates.
These are similar to the “center-arrow coordinates” used in [1]}, [2]}. Then
\({\left\lbrace \begin{array}{ll}w_1=w+u,\\w_2=w-u.\end{array}\right.}\) 
